The invention relates generally to cellular communication networks and, more particularly, to radio planning in cellular communication systems.
Radio planning algorithms are conventionally used in cellular networks, for example, to allocate frequencies to cells. The current trend is to implement increasingly more adaptive radio planning algorithms which permit the radio planning to be done automatically, without requiring manual operations. Adaptive algorithms are also conventionally used to generate cell neighbor lists automatically. Another example of radio planning operations is the setting of signal strength levels.
Some information produced by adaptive radio planning algorithms is needed not only in the node that controls a given base station and cell, but also in neighboring nodes which control neighboring base stations and cells. In the AMPS and PDC standards, the Mobile Services Switching Center (MSC) is exemplary of such control nodes. In the GSM standard, the Base Station Controller (BSC), is exemplary of such control nodes. A cell on the border between two adjacent groups of cells controlled by separate control nodes typically needs information about one or more cells on the other side of the border (in the adjacent group), for various reasons including enabling a mobile station to be handed off efficiently across the border from one border cell to another. In the handoff situation, the current cell needs to know the appropriate control channel frequency of the handoff target cell. Another example reason for exchanging information between cells on either side of a border is to provide a fast way of finding candidate cells for camping.
Many conventional cellular systems (or networks) perform centralized radio planning, including use of adaptive algorithms, in the Operating Support System (OSS). The OSS communicates the radio planning information to the various control nodes, including communicating relevant portions of one control node""s information (for example, border cell information) to another control node, and vice versa. However, disadvantageously, there is no industry-wide standard for communications between OSS and control nodes such as MSCs and BSCs, so the radio planning information is basically updated (i.e., by a network operator) from OSS to the appropriate control nodes.
As the size and complexity of cellular systems increases, the number of borders between cell groups controlled by separate control nodes (and thus the number of border cells) increases. For example, a local office network typically includes a plurality of cells controlled by a control node referred to as a local office network switch. As more local networks are established, the number of borders and border cells increases. These border cells border either cells of other local office networks or cells in systems other than local office networks. With the above-described increasing complexity, the complexity of implementing centralized radio planning (for example, centralized adaptive channel allocation, ACA) in OSS also disadvantageously increases. Moreover, the amount of communications between the OSS and the various control nodes disadvantageously increases.
Some conventional arrangements, for example private networks such as local office networks, permit the radio planning to be decentralized such that each control node performs some of its own radio planning locally rather than receiving it from OSS. However, frequency (e.g., broadcast control frequency) assignments for border cells are set manually (and hence non-adaptively) by the network operator. Changes of frequencies in border cells are then communicated by the network operator to the control nodes associated with the bordering cells. Adaptive frequency allocation for border cells is not conventionally performed by the local control nodes due to fears of network problems that could result. For example, other bordering cells would be immediately affected by any locally originated frequency changes in a given border cell, but conventional network architectures are not capable of immediately providing the frequency changes to the relevant control nodes.
It is therefore desirable in a cellular communication system to provide for more immediate communication of locally originated border cell information to control nodes of bordering cells. This is achieved according to the present invention by communicating the border cell information over conventionally existing communication paths already coupled between control nodes in conventional cellular systems. This permits, for example, a given control node to assign locally its own border cell frequencies, and then report these frequency assignments to the relevant neighboring control node(s).